Illuminated electrical switch



Feb. 2, 1965 w. A. DE sMlDT 3,168,636

. ILLUMINATED ELECTRICAL SWITCH Filed June 2. 1961 2 Sheets-Sheet 1 Bjwg ww I ATTORNEY Feb. 2, 1965 Filed June 2. 1961 W. A. DE SMIDT ILLUMINATED ELECTRICAL SWITCH 2 Sheets-Sheet 2 INVENTOR WOODROW A. DE SMIDT BLZMQ/ fm ATTORNEY United States Patent ilice e 3,158,636 Patented Feb. 2, 1965 The present invention relates to an indicator light assembly useful for application to electrical switches, and which assembly has particular adaptation for use as a temporary testing means for establishing contact engagement at selected operating positions of limit switches or the like, although the same may be applied as a permanent unit in said switches or switches of similar terminal construction.

`The indicator light assembly of the present invention may comprise a base member which may take the form ofa flat insulating plate having at one side thereof one or more indicator lamps, such as a miniature neon-lilled bulb in series connection with a resistor of selected value, and in `\vhich each of the leads of the series connected unit are supported by the plate and make electrical contact with a respectivev terminal in the form of a coil spring supported at the opposite side of the `insulating plate. 'I'he free endsof the `coil spring terminals are each arranged to be positioned in releasable contacting electrical engagement with respective terminal screws of the electrical switch, which screws have preferably been tightened in clamping electrical engagement with appropriate leads of electrical circuit to be controlled by said switch. The coil spring terminals further serve, along with a resilient upstanding stud at the lamp side of the plate, to bias the physical engagement of the terminals with their respective switch terminal screws after a cover member has been secured to the switch housing. The cover is preferably supplied with one or more openings covered with transparent material for observation of the lamp or lamps when the switch contacts have been moved to desired operating position.

. In present day usage some machine tools or` other devices `very often make use of a series of limit switches operating either in sequence or in a variety of relative operating positions, andwhich, at times, are connected with pilot lamps on a control board remote from the switch installation. However, often times it becomes desirable to be able to observe the operation and setting of the switches and their actuators at their attachment position. In addition, although it may not be necessary to have permanent installations of indicator lamps at each switch position, it is highly desirable to be able to set the initial starting position and other control positions of the switch by means of visible indication, such as by means of a removable indicator lamp assembly of the present invention. The present invention therefore further contemplates an auxiliary assembly which may be utilizedas a temporary means for indexing limit switches or the like, and which may be removed after the switches have been so indexed, or which lmay remain in place for visible indication throughout the life of the v switch as a means of checking its operating characteristics or change in settings of its actuator.

Accordingly, it is among the objects of the present invention to provide an indicator light assembly for a switch, which assembly may be connected directly with previously wired terminals of the switch, utilizing a spring contact engageable with `a respective switch terminal, to

" thereby permit either a permanent or temporary installa- Y tion, as desired, the switch cover plate acting` as a re- In the drawings:

` FIG. lis a front elevationalview of a limitswitch (with switch actuator arm removed) embodying the assembly of the present invention;

FIG. 2 is a view substantially the same as thatof FIG. 1, but with the observation cover and other components of the present assembly removed from theswitch;

FIG. 3 is a side elevational view of the switch and indicator lamp assembly of FIG. 1 with parts broken away and parts in section to illustrate the operating relationship between the various cooperating components;

FIG. 4 is a perspective view of the observation cover of this invention, which` view is partially broken away to show construction details;

FIG.` 5 is a perspective view of the insulating plate of the assembly of this invention with operating components mounted thereon;

FIG. 6 is a rear elevational view of the supporting plate ofthis invention, and particularly illustrating the construction of the spring terminals;

FIG..7`is a diagrammatic View of the wiring circuit including the components of the present assembly as used in a precision type limit switch.

Referring now to the drawings, and more particularly to FIGS. l-3, inclusive, it will be seen that the present invention may be embodied in the housing of a conventional limit switch, indicated generally by the reference numeral 20', or in housings of similar switches having a defined arrangement of terminals, such as terminals 21a and 2lb, (see FIG. 2), each being tapped to receive terminal screws 22a and 22b. The operating head 23 of the switch 20 includes a shouldered bearing 24 mounted at one side thereof, which is immaterial to the present invention, and through which protrudes a. control shaft 25. The shaft may include any number oi various combinations of contact arm assemblies (not shown) two variations of which are shown in Patents 2,796,487, and 2,836,081, both being issued to William F. Dehn and assigned to the assignee of the present invention. None of the internal details ofthe switch proper or the operating `head 23 is shown, inasmuch as such details are irnmaterial to the present invention. In fact, it is not neces-` sary that the switch be a limit switch, although the present invention is preferably adapted for use with such switch.

In the case of the presently described switch, the switch housing 20 may be die cast to provide a `cavity 2S forretaining means and as a means for maintaining electrical ,i

Contact with a lamp or lamps included in the assembly.

ceiving an insulating switch base member 29. o The die cast housing 20 may be tapped at the bottom to receive conduit littings in a tapped opening 30. Lead wires 31 o may be connected drectlyto the terminals 21a and 2lb by means 0f the terminal screws 22a and 22b`, as is the normal practice.

The operating head 23 `is provided as `shown in the aforementioned Patent 2,796,487 to be oriented in any one of four directions relative to the switch housing 20. L

It may be secured to the housing 20 in any convenient mannersuchas by means of screws 32, which `also serve to hold in place an L-shapedcover plate 33.` The bearing 24 is secured to the operating head 23 by means ofthe i screws 34. Rotation of the shaft 25 is transmitted to move an insulating actuator point 35, engageable in this casel with a snap-,action precision switch movable contact 36` (see the diagrammatic View of FIG.` 7), the action and description of which are more fully set forth in the aforei 3 mentioned Patent 2,796,487f` As stated previously, the

action of the switch per se does not form a partof the present invention, but has been provided as a convenient means for illustratingthe utility of the indicator assembly of the present invention, as adapted foruse therewith. For purposes of illustration, however, it will be noted that the movable contact 36 of the present switch embodiment ponents of FIGS. 5 and 6 comprise a unitary construction indicated generally by the reference character d0, and which includes a plate-like base member 4]. of insulating material adapted to support one or more miniature indicator lamps 42a and 4212. The lamps 42a, 42h are preferably in the form of neon-lilled bulbs respectively in series connection with an appropriate resistor 43a and 43h. Thus, it will be apparent that such l-amps and resistors provide an inherently high resistance, such that, when this resistance is placed in parallel electrical connection as shown in FIG. 7, with the normally closed contacts Sti, 37b, the lamp 42h will not light. However, upon interrupting the circuit to the station-ary contacts, such as that indicated by the normally open position of contacts 37a, the full line currentwill be 'fed through the circuit of lamp 42a and its resistor 43a to light the lamp llZa. Intermediate the ends of the base 4l there is located an upstanding stud portion 44 of a button 45 of a resilient material, such as natural or synthetic rubber, or the like. The button includes a beveled-shoulder 45 for insertion and retention in an opening in the base 41, which shoulder defines one margin of an annular retaining groove 47. The opposite margin is defined at the underside of the base 41 by means of a retaining and cushioning pad 48.

With reference to the assembly 4t), as shown in FIGS. 5 and 6, it will be observed that one lead of each of the bulbs 42a, i2b is soldered to a grommet or hollow rivet 49 secured to the base 41. The opposite lead is connected directly to a resistor, which in turn, has its opposed lead soldered into a base plate grommet 49. Additional support'is provided by means of grommets Si) at the junction of the lamp leadand its respective resistor lead.

Referring now to the reverse side of the assembly 40, it will be observed that there is soldered to each of the grommets 49 an helically wound spring contact 51. In the case of the limit switch of the present design, eachof the springs S1 are arranged to electrically engage the heads of the terminal screws 22a and ZZb of the precision switchV base 29 upon insertion of the assembly 4t) within the cavity of the switch base 29, as shown in FIG. 3. It is to be noted that the appropriate leads 31 are securely fastened to the terminal screws 22a and 2212, the spring contacts 51 of the assembly d@ are arranged to be placed in secure electrical engagement therewith after being so fastened. More particularly, the spring contacts 51 are adaptable for use in any installation, regardless of whether the terminal leads'are solid or of stranded construction, or whether they terminate in lugs or other types ofconnectors.

The circuit to the respective indicator-lights 42a and 42!) serving the cricuits connectedrespectively to the sets of terminal screws 22a. and 22h is completed by means of the opposing forces exerted by the spring contacts 5l and the button 45 through its upstanding stud portion 4d pressed against the cover plate 6@ when said plate is secured in place byi means of the mounting screws 61 engaging the The springV length will vary to accommodate` the variable heights ofthe terminals screws 22a, b.

The cover plate Gti is preferably of a laminated construction (see FIG. 4) wherein the top plateV 63 may be of a metal stamping having blanked therein observation openings 64a and 64b for lamps 42a and 42h, respectively. Cemented to the top plate 63 is a conforming transparent plate 65 of ?lexiglas or other suitable material. The cover plate dit is further provided with a cushioning gasket do of a material capable of withstanding the effects of moisture, oil and grease or other contaminants which may interfere with effective switch operation.

It will be observed that the assembly illustrated is capable of being placed in permanent installation for use with a limit switch, to indicate the extreme operating positions of said switch. However, Vit will be further appreciated that the assembly 4@ and its cover plate 60 may be used for temporary installation where it is desired to merely observe the initial setting of the limit switchv actuator at its desired operating positions, and

,v thereafter be removed for substitution of a permanent cover plate of the non-indicating type, such as the cover plate shown in the aforementioned Patent2,836,08l.

It will be obvious that the assembly 40 may include only one lamp, when it is desired to indicate only oneL position of a switch capable of receiving saidV assembly,

and that the assembly iii and its cover plate di) may be varied within Wide limits for use as indicators in many types of switch installations without departing from the present invention. The diagrammatic view of FIG. 7. is illustrative of merely one example of 'a typical circuit embodying the lamps 42a, b. There are many variations, including connection of a lamp-resistor unit between terminals Zia and 2lb (not shown) where it is desired to have a single lamp go on when the switch trips from one side to another, especially Where there are more than one limit switches with normally closed contacts arranged in series connection.

I claim! t 1. An electrical switch, comprising the combination of z a housing defining a cavity;

.Y a contact assembly positioned, within saidrcavity and having at least two pairs of opposed stationary contacts, a movable bridging contact adapted for alternative movement to opposed positions for electrically connecting respective pairs of said stationary contacts, and a pairof exposed line terminals mounted on they external surface of said assembly and electrically connected to said stationary contacts;

. an indicator lamp assembly positioned within said cavity and electrically connected to said 'line ter;k minals, said indicator assembly including a supporting base having peripheral dimensions less than the internal peripheral dimensions of said cavity, said base having a rst surface'l facing said terminals and a second surface opposite said iirst surface, atleast two indicating lamp circuits supported .by said supporting base andmounted on said second surface, at least two pairs of resilient conductive contacts disposed on the first surface and respectively in electrical connection with each of said lamp circuits and each of said line terminals;

an observation cover for said switch secured on saidV` housing and over said indicating circuits; and means coacting with said cover and said support- 4ing base for maintaining saidi resilient contacts in biased engagement with respective ones of said terminals.

2. The electrical switch of claim 1, wherein said resilient contacts are in the form of helically coiled springs. 3. The electrical `switch of claim l wherein'said means coacting with said cover and said supporting base cornprises a resilient, stud-like memberprotruding from said second surface and engaged with the inner surface of said cover.

(References on following pave) References Cited in the file of this patent UNITED STATES PATENTS 2,179,198 Reed Nov. 7, 1939 2,193,740 Reed Mar. l2, 1940 5 2,575,820 Linton NOV. 20, 1951 6 Neratko Sept. 18, 1956 Dehn June 18, 1957 Iacaman Feb. 10, 1959 FOREIGN PATENTS France Sept. 11, 1953 

1. AN ELECTRICAL SWITCH, COMPRISING THE COMBINATION OF: A HOUSING DEFINING A CAVITY; A CONTACT ASSEMBLY POSITIONED WITHIN SAID CAVITY AND HAVING AT LEAST TWO PAIRS OF OPPOSED STATIONARY CONTACTS, A MOVABLE BRIDGING CONTACT ADAPTED FOR ALTERNATIVE MOVEMENT TO OPPOSED POSITIONS FOR ELECTRICALLY CONNECTING RESPECTIVE PAIRS OF SAID STATIONARY CON TACTS, AND A PAIR OF EXPOSED LINE TERMINALS MOUNTED ON THE EXTERNAL SURFACE OF SAID ASSEMBLY AND ELECTRICALLY CONNECTED TO SAID STATIONARY CONTACTS; AN INDICATOR LAMP ASSEMBLY POSITIONED WITHIN SAID CAVITY AND ELECTRICALLY CONNECTED TO SAID LINE TERMINALS, SAID INDICATOR ASSEMBLY INCLUDING A SUPPORTING BASE HAVING PERIPHERAL DIMENSIONS LESS THAN THE INTERNAL PERIPHERAL DIMENSIONS OF SAID CAVITY, SAID BASE HAVING A FIRST SURFACE FACING SAID TERMINALS AND A SECOND SURFACE OPPOSITE SAID FIRST SURFACE, AT LEAST TWO INDICATING LAMP CIRCUITS SUPPORTED BY SAID SUPPORTING BASE AND MOUNTED ON SAID SECOND SURFACE, AT LEAST TWO PAIRS OF RESILIENT CONDUCTIVE CONTACTS DISPOSED ON THE FIRST SURFACE AND RESPECTIVELY IN ELECTRICAL CONNECTION WITH EACH OF SAID LAMP CIRCUITS AND EACH OF SAID LINE TERMINALS; AN OBSERVATION COVER FOR SAID SWITCH SECURED ON SAID HOUSING AND OVER SAID INDICATING CIRCUITS; AND MEANS COACTING WITH SAID COVER AND SAID SUPPORTING BASE FOR MAINTAINING SAID RESILIENT CONTACTS IN BIASED ENGAGEMENT WITH RESPECTIVE ONES OF SAID TERMINALS. 